Which factor is critical to ensuring the reliability of defect indications in MPT?

The cleanliness of the test surface is critical to ensuring the reliability of defect indications in Magnetic Particle Testing (MPT) because any contaminants—such as grease, oil, dirt, or rust—can interfere with the proper application and performance of the magnetic particles. If the surface is not adequately prepared, these contaminants can mask defects or create false indications.

In MPT, the process involves creating a magnetic field in the part being inspected. When there are surface discontinuities, the magnetic particles will cluster at these defects, revealing their presence. However, if the surface is dirty, the magnetic particles may not adhere properly, leading to either missed defects or misleading signals, resulting in an inaccurate assessment of the part's integrity. Therefore, maintaining a clean inspection surface is paramount to achieving reliable and accurate results in MPT.

While factors such as the texture of the magnetic particles, their color, and the environmental temperature may have some influence, they do not have the same level of critical impact on the indication of defects as the cleanliness of the test surface.